Inspection circuit



Dec. 31, 1963 R. G. HusoME 3,115,970

INSPECTION CIRCUIT Filed Dec. 5, 1960 2 Sheets-Sheet 1 FIG. IA.

CONSTANT INVENTOR.

VOLTAGE ROBERT e. HUSOME TRANSFORMER ATTORNEYS.

BY a. I

- United States Patent 3,115,970 INSPECTION CIRCUIT Robert G. Husome,Manhattan Beach, Calif., assignor, by mesne assignments, toBarry-Wehmiller Machinery Filed Dec. 5, 1960, Ser- No. 73,689 Claims.(Cl. 2t)9111.5)

This invention relates to apparatus for inspecting empty bottles forcleanliness and, more particularly, to improvements in the electricalcircuits employed therewith.

A preferred method for inspecting empty bottles for cleanliness is topass these bottles through an inspection zone, which at one side has asource of illumination, usually at the base side of the bottle, and atthe neck side contains a photocell arrangement. The presence of dirt orforeign and undesired particles in the bottle is usually sensed by thefact that the illumination falling upon the photocell means isdecreased, in response to which detection apparatus is actuated. One ofthe problems arising with this type of arrangement is that the moresensitive the photocell means are made for the detection of foreignparticles, the steadier the source of illumination which must bemaintained to avoid false rejects, and maintaining an illuminationsource steady or constant provides difficulties. Either, sacrifices mustbe made in the desired sensitivity for the photocell means, or someeffort by way of voltage-regulating apparatus for maintaining theillumination constant must be made.

An object of this invention is to provide a novel detection circuitarrangement which automatically compensates for illumination variationwhile permitting optimum sensitivity to be employed for the photocelldetecting means.

Another object of this invention is the provision of a novel andimproved circuit arrangement for automatically compensating photocelldetecting means for variations in an entire illumination field.

Still another object of the present invention is the provision of novelcircuitry which is actuated in response to the photocell detecting meansfor rejecting or accepting a bottle which eliminates the necessity forauxiliary apparatus for detecting when a bottle is in the inspectionzone.

These and other objects of the invention may be achieved in anarrangement wherein the output from each of a plurality of photocells,which are disposed to receive light which has been passed through abottle, are each applied to a separate amplifying means. The outputs ofall these amplifying means are combined and used to control theoperating potential applied to all of these photocells in a manner tomaintain their over-all output constant, despite variations in the levelof illumination of the entire field. This, however, does not prevent theoutput from any one or more of these photocells, which varies due to thepresence of foreign particles, from being detected. Means are providedwhich are actuated to reject a bottle only in response to the output ofthe detecting means. These last means effectively include a capacitorwhich is charged up. When a clean bottle is in the inspection zone, thiscapacitor is discharged. Such discharge is prevented, however, in thepresence of an output from the detecting means. The capacitor, after aninterval sufficient to permit a complete inspection of the bottle, isconnected to a reject mechanism. If the capacitor remains charged, thisreject mechanism is actuated.

The novel features that are considered characteristic of this inventionare set forth with particularity in the appended claims. The inventionitself, both as to its organization and method of operation, as well asadditional objects and advantages thereof, will best be understood fromthe following description when read in connection with the accompanyingdrawings, in which:

FIGURE 1 is a sectional view of bottle-inspection apparatus of the typesuitable for employment with this invention;

FIGURE 1A is a plan view of a starwheel used with the apparatus shown inFIGURE 1;

FIGURE 2 shows an arrangement of photocells which are suitable foremployment with this invention; and

FIGURE 3 is a circuit diagram of an embodiment of the invention.

The handling of bottles so that they may be passed into and out of aninspection zone and be rejected, if necessary, may be performed mosteasily by a multipocket starwheel, which overhangs the conveyor suchthat bottles.

are momentarily passed off the conveyor for inspection. A preferredarrangement is shown which is derived from principles thoroughlydescribed in Patent No. 2,800,226. Accordingly, the details of thisinspection machine are only suggested in FIGURE 1, which is a sectionalview of an embodiment thereof. A bottle 10 is carried through aninspection zone by a pair of starwheels 14A, 14B, having pockets 14A,14B formed therein for the purpose. The starwheel is attached to a rotor15 to be driven. For each pocket in the starwheel there is provided asuction cup 12. A vacuum can be applied to this cup through a passageway13 connected through a valve passageway 13A to a vacuum source, notshown. A valve 17, shown in its nonreject position, normally preventsthe vacuum from being applied to a suction cup.

A bottle is moved by the starwheel from a conveyor, through the bottleinspection zone, and then back to the conveyor, or moved to a rejectbottle accumulator, not shown. A bottle is held properly in theinspection position over a light source 16 by a spring-loaded bar 19.The starwheel pair 14A, 143 may be changed for runs of different bottlesizes. The bottle 10 in FIGURE 1 is shown being held in the inspectionzone. At one side of this inspection zone is a high-intensityincandescent-light source 16, which usually is positioned opposite thebottom of the bottle 10. Since photoelectric cells are being employedfor performing the foreign-matter-detection function, variations inintensity of the light source can cause reactions akin to that caused byforeign matter in a bottle, as far as detection function by thephotocells is concerned. This may be minimized to a certain extent,although not completely eliminated, by employing a constant-voltagetransformer 18, through which power is applied to the light source 16.

The illumination from the light source 16 passes through a diffusedopalized glass 24. The function of this glass is to eliminate any falsedetection which may be occasioned by shadowing of lettering which mayappear in the bottom of a bottle. The change in intensity of light ofany given photocell, due to the imaging of the smallest particle offoreign matter which is to be detected,

is far greater than the random fluctuations of light intensity on anyphotocell caused by variations in glass thickness and light transmissionbetween clean bottles of a given type.

Light rays from the bottom of the bottle are collimated by a lens as.The focal length of this lens is equal to the distance of the lens fromthe bottom of the bottle. The collimated rays then pass through a prism28. A preferred type of prism is known as the dove prism. This opticalcomponent is sometimes called an inverting prism. It is necessary thatapproximately plane wave fronts be passed through the prism; otherwise,the image on one side of the prism of an object on the other side of theprism will be distorted. The dove prism is mounted in a holder 30,which, in turn, is supported by bearings 32, 34. The holder of theprism, and therewith the prism, is rotated above the center by means ofa belt 36 which passes over the holder 30 and is driven by a pulley 40,which, in turn, is driven by a motor 42.

The collimated light output from the prism is focused, in turn, byanother lens 44 upon several photocells supported in a holder 50. InFIGURE 1 the leads 52 of the several photocells may be seen. Thefunction of the lens 44 is to form an image of the bottom of the bottleon the photocells. The prism serves to rotate the image about its axisof symmetry. The image rotates at a speed which is twice that of theprism. It should be noted that the lenses 26 and 44 are supported inholders 27, 45 on a shaft 54. Each holder may have several lenses, ifdesired. The holders are indexed on the support shaft such that any pairof lenses may be aligned concentric with the prism by rotating the shaftand providing a suitable detent. The lens system must be changed toaccommodate different bottle heights and diameters. The entireinspection-head structure may be raised or lowered so that the bottomlens just barely clears the bottle. In order to satisfy the requirementof approximately plane wave fronts through the prism, the bottle lens issuch that its focal length is just slightly greater than the height ofthe bottle being inspected. The focal length of the top lens must besuch that a constant image diameter is maintained for different bottlesizes.

A small starwheel 56 engages the neck of each bottle which is passedthrough the inspection zone. FIGURE 1A is a plan view of this starwheel.The starwheel 56 is mounted on a shaft 58, which rotates as a result bybeing engaged by the bottle passing into and out of the inspection zone.Each time a bottle enters the inspection zone and leaves the inspectionzone, a switch 134 is operated. The details of such operation areexplained in connection with the explanation of FIGURE 3.

Reference is now made to FIGURE 2, which is a view looking up at thepattern of several photocells. It will be seen that a plurality ofphotocells 64A, 64B, 64C, 64D, and 64E are employed for scanning theimage of the bottom of the bottle. The photocell pattern preferably issuch that the image of the bottom of the bottle may be completelyinspected during one rotation of the image about its center.

The light which passes through a bottle which is in the inspection zonefalls upon the photocells. The arrangement of the photocells is suchthat a complete scan of the image is made during one rotation. Anypattern of photocells may be chosen as long as every radial increment ofthe image circle is overlapped by one or more of the photocells when theimage is rotated 360 about its axis of symmetry.

The photocells are wired into a circuit such that, when any one of themis momentarily occulted by a dark spot in the image caused by foreignmatter obscuring part of the uniform illumination beneath the bottle,the output voltage changes by a percentage which can be detected. Sincethe image rotates very rapidly, it is essential that the photocells beof a type with a very short time constant. For reliable operation, it isalso necessary that the photocells be fairly sensitive, i.e., that theyhave a reasonable light to dark current ratio. The change in photocelloutput voltage manifests itself as a short pulse. This pulse isamplified and eventually is enabled to operate a relay amplifier toreject the bottle.

The descriptions which have been made thus far are substantially thoseof FIGURES l and 2 which appear in an application for aBottle-Cleanliness Inspection Apparatus, by James H. Wyman, filed April11, 1960, hearing Serial No. 21,164, and which is assigned to a commonassignee. The novel features of this arrangement are claimed therein.The foregoing description has been inse rted by Way of providing adescription of a suitable arrangement for utilizing the novel circuitryto be described. However, this preceding description of the photocelldetection means should not be construed as a limitation upon thisinvention, since it will be apparent to those skilled in the art thatother photocell arrangements may utilize the embodiment of thisinvention without departing from the spirit and scope thereof.

Reference is now made to FIGURE 3, which shows a circuit diagram of anembodiment of this invention. The photocells employed in an embodimentof the invention which was built were of the type known as photodiodes,which have the characteristic that their resistance decreases withincreasing illumination. One side of all these photodiodes is connectedto ground. A bias potential is applied to the other side of thesephotodiodes from a potential source 70. This is applied through aresistor 72 and through a switch 74 to one side of a plurality ofpotentiometers, respectively 76A, 76B, 76C, 76D, 76E. A resistor 78A,78B, 78C, 78D, 78E connects the other side of each of the potentiometersbearing the associated letters to the respective photocells 64A, 64B,64C, 64D, 64E. The slider arm of each of the respective potentiometersis connected to the side of the potentiometer to which potential isapplied.

The ungrounded sides of the respective photodiodes 64A through 64E areconnected to the bases of associated NPN-type transistors 80A through80E. Effectively, these transistors act as amplifying devices foramplifying the outputs from the respective photodiodes. The collectorsof the respective transistors fiA through SIDE are connected togetherand to the source of operating potential 70. Each one of the emitters ofthe respective transistors is connected to a separate resistor 84A, 84B,34C, 84D, and ME. Each one of these emitters is also connected to anassociated diode, respectively 86A, 86B, 86C, 86D, and 86E.

The ends of the resistors 84A through 84E which are not connected to therespective transistor emitters are connected together and to the base ofan NPN-type transister 83. The base of this transistor is also connectedthrough a resistor 90 to ground. The cathodes of the respective diodes86A through 86E are connected to the base of an NPN-type transistor 92.The base of this transistor is also connected through a resistor 94 toground. The emitter of transistor 88 is connected to a potentiometerwhich is connected in series with series-connected resistors,respectively 98, 1%, and 1492. These serve to provide a voltage divider,whereby a bias signal may be derived for the emitter of transistor 83.The resistor '72 is connected to serve as a load resistor for thecollector of transistor 88, besides being connected to switch 74.

The emitter of transistor 92 is connected through a resistor 164 toground. Transistor 92 also receives a biasing potential through aresistor 166 which is connected from the emitter of the transistor tothe potential source '70. The collector of transistor 92 is connectedthrough a first resistor 1% to the base of a PNP-type transistor 116 Theresistor W8 is connected to another resistor 112, which is connected tooperating potential source 76. Therefore, the collector of transistor 92receives operating potential through resistors 112 and 108, which areconnected in series.

Transistor has its emitter connected to the potential source 70. Itscollector is connected through a first resistor 116 to the base of anNPN-type transistor 118 and through a second resistor 120 to ground. Thetransistor 118 has its emitter connected through a diode 122 to ground.The collector of transistor 118 is connected through a resistor 126 tothe source of operating potential '70 and also to the emitter of aunijunction transistor 124. The first base B1 of the unijunctiontransistor 124- is connected to a resistor 128, the other side of whichis connected to ground. The second base B2 of the unijunction transistoris connected to the source of operating potential 70. The controlelectrode of a silicon control rectifier 130 is connected to the firstbase of the unijunction transistor 124. The cathode of the siliconcontrol rectifier is connected to ground. The anode of the siliconcontrol rectifier is connected through a resistor 132 to one contact134D on a switch 134. The other contact 134C of the switch 134 isconnected through a resistor 136 to the source of operating potential. Acapacitor 138 is connected from the emitter of the unijunctiontransistor to ground.

The swinger arm of the switch 134 is connected through a capacitor 140to ground. The switch 134, it will be noted, has four contacts,respectively 134A, 1343, 134C, and 134D. In the position shown in thedrawing, the swinger connects together contacts 134A and 13413. It alsoconnects them to the capacitor 140. The switch 134 is operated by thesmall starwheel 56 and shaft 53 in the manner shown in FIGURE 1. Whenthere is no bottle present in the inspection zone, the swinger arm ofthe switch 134 remains in the position shown in the drawing, wherein itconnects with contacts 134A and 134B. When a bottle moves into theinspection zone, the starwheel 56 is rotated and moves the swinger armof the switch to make contact with terminals 134C and 134D. When thebottle moves out of the inspection zone, starwheel 56 rotates again torestore the swinger arm to the position shown in the drawings.

The solenoid 142 of a reject relay has one end connected to the contacts134A, 134B and the other end connected to ground. The contacts 142A areconnected to reject apparatus 144, which is rendered operative whenthese are closed.

Each one of the potentiometers 76A through 76B is adjusted to correctfor unequal photocell sensitivities. The five transistors 80A through WEare connected as emitter followers to the base of transistor 88. Thepotential at each one of these transistor emitters is controlledprimarily by the amount of light striking its associated photocell. Adecrease in light results in a positive-going emitter voltage. Thevoltage applied to the base of transistor -88, which acts as a commonamplifier, is efiectively equal to the sum of the emitter currents oftransistors 811A through Sit/E, which are connected to this base andthrough resistor to ground. As a result, the voltage which is appliedacross the photodiodes and to the base of transistors 811A through 811Ewill be a function of the average illumination received by all thephotodiodes 64A through 64E, with a decrease in illumination resultingin a positive-going voltage being applied to the base of transistor 88.

Transistor 88 is connected as a common emitter ampliher and is driven bythe voltage applied to its base. The sensitivity of transistor 88 may beadjusted by the potentiometer 96. Adjustments of the potentiometers 76Athrough '7 6E are made with the switch 7 4 operated to the adjustposition. With the switch '74 in the operating position, the currentdrawn through the collector of transistor 38, which is determined by theaverage illumination, effectively determines the potential being appliedto the potentiometer 76A through 76E. Thus, when the illumination levelchanges, this is sensed by transistor 8'3. The voltage applied acrossthe otentiometers 76A through 7 6E, and thereby the voltage which biasesthe five photodiodes, is changed to compensate for the change inillumination.

The circuit described provides a feedback loop in which the voltageapplied to the base of the transistor 88 will remain essentiallyconstant with Widely varying illumination levels. The voltages on theemitters of transistors 86A through 81113, however, will vary primarilyas the result of their respective photocells observing a differentamount of light than the average light of all the photocells. Thecircuit therefore becomes primarily contrast sensitive rather thanillumination-level sensitive.

The emitters of transistors 80A through 80E, as has been previouslydescribed, are connected through diodes 86A through 861-3 to the base oftransistor 92. As a result, the voltage applied to the base of thistransistor will represent at any instant the darkest portion of theimage under examination. In view of the positive bias applied to theemitter of transistor 92, the voltage applied to its base must exceed apredetermined positive level before the transistor 92 can startconducting. Thus, transistor 92 provides an output signal whenever anyone or more of the transistors 811A through E respond to a change in thelevel of illumination applied to their respective photocells in responseto the presence of a foreign particle.

The output of transistor 92 is amplified by transistor 1119. Transistor118 operates as a shorting switch for discharging capacitor 138 whenevertransistor 113 is rendered conductive by an output from transistor 110.The silicon diode 122 in the emitter circuit of transistor 118 servesonly to bias the emitter slightly positive (by an amount equal to theforward voltage drop of the diode approximately 0.65 volt), so as toreduce the collector leakage of transistor 118.

Unijunction transistor 124, resistor 126, and capacitor 133 form arelaxation oscillator whose period of oscillation is five milliseconds.This corresponds to the time required for one complete optical scan ofthe bottle under inspection. Each time the unijunction transistor fires,it discharges capac'tor 138 and generates a pulse across resistor 123.This pulse is applied to the control electrode or injector of thesilicon control rectifier .130. The capacitor 138 may also be dischargedby transistor 118 whenever it is rendered conductive in response to asignal from the preceding transistors. Unijunotion trarisistor 124 willbe rendered conductive only if transistor 118 remains nonconductive fora period equal to a period of five milliseconds. That is the amount oftime required to charge up capacitor 138 to the voltage value necessaryto render unijunotion transistor 124 conductive Thus, during eachinspection cycle the unijunotion transistor will become conductive onlyif an accept condition exists, i.e., no signal indicative of thepresence of dirt in a bottle under inspection is received.

The sequence of events during each inspection cycle is essentially asfollows:

( 1) A bottle approaches the optical axis of the scanner. The neck ofthe bottle advances the turnstile, which causes the trigger switch 134to swing from contacting terminals 134A, 1348 to terminals 134C, 134D.

(2) Capacitor 149 is connected to resistor 136 and resistor 132. Thiscapacitor charges up through resistor 136.

(3) When the bottle reaches the center of the optical axis, one of twoconditions can exist: either (a) the bottle under the inspectioncontains opaque matter, a rejection exists, transistor 11% is notmaintained nonconductive for a period of five milliseconds, wherebyvoltage across capacitor 138 never reaches a level high enough to renderunijunetion transistor 124 conductive; or b), the bottle underinspection is clean, an accept condition exists, transistor 118 isturned off for at least one optical scan, or five milliseconds, and thevoltage on capacitor 138 reaches a level high enough to fire transistor124. As a result of the transistor 124 being conductive, a control pulseis injected into the silicon control rectifier to render it conductive,whereby it can rapidly discharge capacitor 140 or reduce it to anextremely low value.

(4) As the bottle continues to move past the optical axis it furtheradvances the turnstile, which returns the switch 134 to its positionshown in the drawings. If a reject condition has existed, capacitor 140is fully charged, and this voltage is applied to relay 142 to energizeit and cause it to operate the reject mechanism 144. If the bottle whichis passed through the inspection zone has not had any dirt or has beencleaned, then capacitor 140 has been discharged and has insufficientvoltage to energize the relay 142 when it is connected thereto.

As a result of the circuitry which comprises this embodiment of theinvention, not only is compensation made for the average illuminationvariations of the field of illumination applied to the bottle, but,also, it is not necessary to specifically detect when a bottle is beinginspected. The oscillator formed by the resistor 126, capacitor 133, andunijunction 124 establishes a detection interval, and, if a bottleduring that interval can pass inspection, then the reject mechanism isnot operated.

There has accordingly been described and shown herein novel and usefulcircuitry for employment with bottle-inspection apparatus. The types oftransistors and photodiodes shown are for purposes of illustration, andnot to be construed as a limitation upon the invention.

I claim:

1. An improved circuit for a system for inspecting an empty bottle forcleanliness of the type wherein a bottle passes through an inspectionzone including a source of illumination on one side and a plurality ofphotocells on the other side, said circuit comprising a transistorhaving base, collector, and emitter electrodes, a resistor having oneend connected to said transistor collector, means connected to the otherend of said resistor for applying operating potential to saidtransistor, means for applying operating potential to said photocellsfrom said transistor collector, means for combining all the outputs ofsaid photocells; means for applying said combined photocell outputs tothe base of said transistor for varying the current drawn by saidtransistor through said resistor to maintain the level of the combinedphotocell outputs substantially constant, means for detecting avariation in the output of one of said photocells due to the presence ofan undesired foreign particle in a bottle being inspected, and means forrejecting said bottle responsive to an output from said means fordetecting.

2. An improved circuit as recited in claim 1 wherein said means forcombining all the outputs of said photocells comprises a plurality oftransistors each having a base, emitter, and collector electrode, meansconnecting the output of a different one of said photocells to the baseof a different one of said transistors, means including a resistorconnecting the emitters of each of said plurality of transistors to thebase of said transistor, and means for applying operating potentialbetween collectors and emitters of said plurality of transistors.

3. An improved circuit for a bottle inspection system of the typewherein a bottle passes through an inspection zone including a source ofillumination on one side and photocell means on the other, said circuitcomprising a capacitor, means for charging said capacitor, means fordischarging said capacitor when its charge exceeds a fixed level, meansfor detecting an output from said photocell means indicative that abottle should be rejected and producing an output signal indicativethereof, shorting switch means for preventing said capacitor fromcharging up to said fixed level in the presence of said output signal,and means operated responsive to said capacitor not attaining said fixedcharge level for rejecting said bottle.

4. An improved rejection circuit for a bottle inspection system of thetype wherein a bottle passes through an inspection zone including asource of illumination on one side and photocell means on the otherside, said circuit comprising a first capacitor, means for charging saidfirst capacitor, means for discharging said capacitor when its chargereaches a predetermined level, a discharge transistor having base,emitter, and collector electrodes, means connecting said dischargetransistor collector and emitter electrodes across said first capacitor,means for detecting an output from said photocell means indicative thata bottle should be rejected and producing an output signal indicativethereof, means for applying said output signal to the base of saidtransistor to render it conductive to thereby prevent said capacitorfrom charging to said predetermined level, a second capacitor, means forcharging said second capacitor, means for discharging said secondcapacitor responsive to said first capacitor being discharged, and meansresponsive to said second capacitor being charged for rejecting abottle.

Q as

5. An improved rejection circuit for a bottle inspection system asrecited in claim 4 wherein said means for discharging said firstcapacitor when its charge reaches a predetermined level comprises aunijunction transistor having an emitter, a first and a second base, aresistor having one end connected to said first base, means connectingsaid first capacitor between said unijunction transistor emitter and theother end of said resistor; said means for discharging said secondcapacitor responsive to said first capacitor being discharged comprisesa siliconcontrolled rectifier having a control electrode connected tosaid first base, a cathode connected to said resistor other end, and ananode, and means connecting said second capacitor between saidsilicon-controlled rectifier anode and cathode.

6. An improved circuit for a system for inspecting an empty bottle forcleanliness of the type wherein a bottle passes through an inspectionzone including a source of illumination on one side and a plurality ofphotocells on the other, said circuit comprising means for combining theoutputs of all said photocells, means for maintaining the value of thecombined outputs of said photocells substantially constant, means fordetecting a variation in the output of a photocell due to the presenceof an undesired foreign particle in a bottle being inspected andproviding an output signal indicative thereof, a capacitor, means forcharging said capacitor, means for periodically discharg ing saidcapacitor, means responsive to said output signal to render said meansfor periodically discharging said capacitor inoperative, and meansresponsive to said capacitor being charged to reject a bottle which hasbeen inspected.

7. An improved circuit for a system for inspecting an empty bottle forcleanliness of the type wherein a bottle passes through an inspectionzone including a source of illumination on one side and a plurality ofphotocells on the other side, said circuit comprising means forcombining the outputs of all said photocells, means for maintaining thevalue of the combined outputs of said photocells substantially constant,means for detecting when the output of one of said photocells is altereddue to the presence of unwanted opaque matter in a bottle beinginspected and for providing an output signal indicative thereof, acapacitor, means for charging said capacitor, means for discharging saidcapacitor when its charge reaches a predetermined level, means forpreventing said capacitor from charging up to said predetermined levelresponsive to said output signal, and means operated responsive to saidcapacitor not attaining said predetermined level for rejecting saidbottle.

8. An improved circuit as recited in claim 7 wherein said means forcombining the outputs of all said photocells comprises a plurality oftransistors each having a base, emitter, and collector electrode, meansconnecting the output of a different one of said photocells to the baseof a diiierent one of said transistors, means including connecting theemitters of each of said transistors to a common junction, said meansfor maintaining the value of the combined outputs of said photocellssubstantially constant comprises a control transistor having base,emitter, and collector electrodes, means for applying operatingpotential to said control transistor including a resistor connected inseries with the collector of said control transistor, and means forapplying operating potential to said photocells including a connectionfrom the collector of said control transistor to said photocells.

9. An improved circuit as recited in claim 7 wherein said means fordischarging said capacitor when its charge reaches a predetermined levelcomprises a unijunction transistor having an emitter and a first andsecond base, a resistor having one end connected to said first base,means connecting said capacitor between said unijunction transistoremitter and the other end of said resistor; said means for preventingsaid capacitor from charging up to said predetermined level includes atransistor having an emitter and collector between which said capacitoris connected, and a base to which said output signal is applied.

10. An improved circuit for a system for inspecting an empty bottle forcleanliness of the type wherein a bottle passes through an inspectionzone including a source of illumination on one side and a plurality ofphotocells on the other side, said circuit comprising a transistorhaving base, collector, and emitter electrodes, a resistor having oneend connected to said transistor collector, means connected to the otherend of said resistor for applying operating potential to saidtransistor, means for applying operating potential to said photocellsfrom said transistor collector, means for combining all the outputs ofsaid photocells, a plurality of transistors each having a base, emitter,and collector electrode, means connecting the output of a different oneof said photocells to the base of a different one of said transistors,means including a resistor connecting the emitters of each of saidplurality of transistors to the base of said transistor, means forapplying operating potential between collectors and emitters of saidplurality of transistors, means for detecting a change in output of anyof said photocells due to the presence of an undesired opaque particlein a bottle being inspected and producing a rejection signal including aseparate diode coupling each of the emitters of said plurality oftransistors to a junction, and amplifying means connected to saidjunction, a first capacitor, means for charging said first capacitor, adischarge transistor having base, emitter,

and collector electrodes, means connecting said discharge transistorbase to said junction, means connecting said first capacitor betweensaid discharge transistor base and collector, means for discharging saidfirst capacitor when its charge reaches a predetermined level comprisinga unijunction transistor having an emitter and a first and second baseelectrode, a resistor having one end connected to said first base, meansconnecting said first capacitor between said unijunction transistoremitter and the other end of said resistor, a silicon-controlledrectifier having an anode, cathode, and control electrode, meansconnecting said silicon-controlled rectifier control electrode to saidunijunction transistor first base, means connecting saidsilicon-controlled rectifier cathode to said other end of said resistor,a second capacitor, means for charging said capacitor, means forrejecting a bottle after inspection operative responsive to said secondcapacitor being charged up, and switch means operative responsive to abottle entering said inspection zone for connecting said secondcapacitor to said means for charging said capacitor and across saidsilicon-controlled rectifier anode and cathode and responsive to saidbottle leaving said inspection zone for connecting said second capacitorto said means for rejecting a bottle.

Weathers July 6, 1943 Bliss Feb. 18, 1958

1. AN IMPROVED CIRCUIT FOR A SYSTEM FOR INSPECTING AN EMPTY BOTTLE FORCLEANLINESS OF THE TYPE WHEREIN A BOTTLE PASSES THROUGH AN INSPECTIONZONE INCLUDING A SOURCE OF ILLUMINATION ON ONE SIDE AND A PLURALITY OFPHOTOCELLS ON THE OTHER SIDE, SAID CIRCUIT COMPRISING A TRANSISTORHAVING BASE, COLLECTOR, AND EMITTER ELECTRODES, A RESISTOR HAVING ONEEND CONNECTED TO SAID TRANSISTOR COLLECTOR, MEANS CONNECTED TO THE OTHEREND OF SAID RESISTOR FOR APPLYING OPERATING POTENTIAL TO SAIDTRANSISTOR, MEANS FOR APPLYING OPERATING POTENTIAL TO SAID PHOTOCELLSFROM SAID TRANSISTOR COLLECTOR, MEANS FOR COMBINING ALL THE OUTPUTS OFSAID PHOTOCELLS; MEANS FOR APPLYING SAID COMBINED PHOTOCELL OUTPUTS TOTHE BASE OF SAID TRANSISTOR FOR VARYING THE CURRENT DRAWN BY SAIDTRANSISTOR THROUGH SAID RESISTOR TO MAINTAIN THE LEVEL OF THE COMBINEDPHOTOCELL OUTPUTS SUBSTANTIALLY CONSTANT, MEANS FOR DETECTING AVARIATION IN THE OUTPUT OF ONE OF SAID PHOTOCELLS DUE TO THE PRESENCE OFAN UNDESIRED FOREIGN PARTICLE IN A BOTTLE